"I am the living
bread that came down from heaven; whoever eats this bread will
live forever; and the bread that I will give is my flesh for the
life of the world."(John 6:51)

The other Sacraments give us grace, the
Holy Eucharist gives us not only grace but the Author of all grace,
Jesus, God and Man. It is the center of all else the Church has and
does.
As St. Mark records that, at the Last Supper, Jesus "took bread,
blessed and broke it and gave it to them: "Take this, this is my Body"
(Mk 14:22). That word blessed in Greek is eucharistesas, from
which the Eucharist derives its name.
Three of the four Gospels record the institution of the Holy Eucharist:
Matthew 26:25-29; Mark 14:22-25; Luke 22:19-23. St. Paul also records it
in First Corinthians 11:23-25. St. John's Gospels does not report this,
presumably because he intended chiefly to fill in what the others had
not written, for he wrote probably between 90 and 100 A.D. There are
small variations in the words, but the essentials are the same in all
accounts: This is my body... this is my blood.
In John 6:53 Jesus said: "Unless you eat the flesh of the Son of Man
and drink His blood you will not have life in you." Of course, He
did not mean to cut off salvation from those who through no fault of
their own do not know or grasp this truth. It is like the case of
Baptism: one must receive it if one knows.
The form, that is the words required for the Eucharist, are of course
the words of institution. The matter is wheat bread (white or whole
wheat) for the host, and natural wine (mixed with a very little water)
for the chalice. Addition of a notable amount of other matter would make
the material invalid.
Jesus is present wherever the appearances (species) of bread and wine
are found after the consecration. Hence He is found even when the host
is divided. The substance of bread and wine is gone, only the
appearances remain. The Church calls this change transubstantiation:
change of substance.
In John 6:47-67 Jesus did not soften His words about His presence even
when so many no longer went with Him: had He meant only that bread and
wine would signify Him, He could have so easily explained that, and they
would not have left.
The Church has always understood a Real Presence. For example, St.
Ignatius of Antioch, who was eaten by the beasts in Rome around 107
A.D., wrote: "The Eucharist is the flesh of our Savior Jesus Christ"
(To Smyrna 7:1). St. Justin the martyr wrote around 145 A. D: "We have
been taught that the food is the flesh and blood of that Jesus who was
made flesh" (Apology 1. 66. 2). The Council of Trent in 1551 defined
that Jesus is really present in the Eucharist, body and blood, soul and
divinity.
Obviously, this divine presence deserves our worship. Really, someone
who believes in it should be much inclined to come before the tabernacle
often. Benediction with the Blessed Sacrament seems to have started in
the 15th century. The Church also promotes Forty Hours devotion. In some
places there is perpetual adoration. - Fr. William G. Most